In the early 1970's Motor Wheel Corporation of Lansing, Mich., assignee of applicant herein, as well as its then parent company, The Goodyear Tire & Rubber Company of Akron, Ohio, developed and introduced an improved form of composite metal-elastomer styled wheel marketed under the registered trademark "POLYCAST". Such styled wheels provided an automotive type wheel in which metallic parts of simple, conventional configuration, for which manufacturing equipment was already available, are utilized as the basic structural components to thereby obtain a high strength standardized wheel construction at minimum cost. The aesthetically pleasing appearance was imparted to this standard steel backbone by a permanently adhered ornamental plastic body, either molded separately or in-situ as a homogeneous one-piece body, or in the form of a plastic cover secured by an adhesive foam body to the outboard side of the wheel. This provided an improved anti-noise characteristic to the wheel and enabled the appearance of the wheel to be readily and economically varied to suit different customer's styling requirements without varying the basic structural components of the wheel. Additional benefits resided in the side impact cushioning to prevent damage to the wheel while retaining the high strength and impact resistance advantages of the time-proven conventional ductile steel wheel components. Wider variations in styling and contour configurations were also obtained than were possible in the previous deep drawn styled all-steel wheels. The serious problems of loss and theft of removable wheel covers were also eliminated.
Various embodiments of such "POLYCAST" wheels, as well as methods and apparatus for producing the same, are set forth in the following United States Patents and pending patent applications assigned to the assignee herein, which are incorporated herein by reference:
______________________________________ U.S. Pat. No. 3,669,501 6/1972 Derleth U.S. Pat. No. 3,756,658 9/1973 Adams U.S. Pat. No. 3,762,677 10/1973 Adams U.S. Pat. No. 3,815,200 6/1974 Adams U.S. Pat. No. 3,918,762 11/1975 Hampshire U.S. Pat. No. 3,794,529 2/1974 Thompson U.S. Pat. No. 3,935,291 1/1976 Jackson U.S. Pat. No. 3,956,451 5/1976 Adams U.S. Pat. No. 4,398,770 8/1983 Smith U.S. Pat. No. 4,659,148 4/1987 Grill U.S. Pat. No. 4,682,820 7/1987 Stalter U.S. Pat. No. 4,786,027 11/1988 Stalter U.S. Pat. No. 4,290,605 12/1988 Stalter U.S. Pat. No. 4,847,030 7/1989 Stalter U.S. Pat. No. 4,861,538 8/1989 Stalter ______________________________________
Other prior art patents issued to unrelated parties and directed to various facets of such styled composite metal and plastic wheels include U.S. Pat. Nos. 3,823,982 and 3,998,494 as well as British Patent 1,290,946 (1972).
In one embodiment of the manufacture of such POLYCAST wheels, a portion of the mold comprises a conventional metal vehicle wheel having a drop center rim secured to a central disc or body having the usual bolt circle holes and a central aperture so that the disc can be mounted on an axle, drum or disc brake assembly. The metal wheel is employed in conjunction with an upper back-up clamp and lower mold part to define therewith a sealed cavity for molding and attaching a three-dimensional contoured plastic overlay, the overlay thus being molded in-situ and permanently attached to the outboard side of the wheel in the mold apparatus. Preferably, the wheel forms the upper surface of the mold cavity and a reaction mixture of a urethane elastomer liquid adhesive material is injected or poured into the mold to fill the cavity and contact the outboard surface of the wheel assembly. The urethane material solidifies to form a high density non-cellular elastomer body which permanently adheres to the outboard surface of the wheel subassembly. The plastic overlay may also be molded from a lower density microcellular closed cell urethane elastomer adhesive material, or a separate decorative cover may be pre-formed and permanent adhesively adhered to the steel wheel subassembly. If the urethane material embodiment is employed, the urethane is allowed to solidify in the mold cavity and then the mold is opened so that the wheel with the overlay securely adhered to it may be removed from the mold. The overlay may then be painted or otherwise covered with a decorative coating to provide a finished metallic-appearing ornamental wheel. The urethane elastomer thus forms a plastic body having a three-dimensional contour which is permanently attached to the outboard side of the wheel to provide a decorative surface, and the elastomer overlay appears to be an integral portion of the metal wheel.
Current styling trends for automotive passenger car wheels have moved in the direction of a so-called "full-face" appearance for the outboard side of the wheel, in which the outboard face appears to have a disc or body which extends from the center of the outboard face radially all the way out to the rim retaining flange for the outboard tire bead. Current styling is also trending toward moving the wheel vent windows or openings radially outward closer to the outer perimeter of the outboard face of the wheel. Such styles can be achieved without much difficulty by using removable wheel covers while still preserving functional vent windows for circulation through the outboard face of the wheel. Such styling can also be achieved in a styled "all steel" wheel pursuant to the teachings of U.S. Pat. No. 4,610,482, issued Sept. 9, 1986, in the names of Overbeck, Lawrence and Golata, assigned to the assignee of record herein.
Moreover, within given limits, such "full-face" styling can also be achieved in the aforementioned prior art "POLYCAST" wheels, as shown for example in the embodiment of FIG. 9 of the aforementioned Adams U.S. Patent No. 3,762,677. However, this has required the use of a relatively thick cross-section in the outer peripheral portion of the urethane body covering the radially inner face of the rim and extending up to the outboard tire-bead-retaining flange of the rim, due to inherent limitations in the injection pouring, molding and de-molding of the urethane reaction mixture. This heavy or large thickness dimension of the urethane material at the outboard tire bead retaining flange of the rim in turn required specialized wheel weights, which also added to the cost and complexity of the wheel. On the other hand, if the urethane material were terminated short of the outboard tire bead retaining flange of the rim to provide a so-called "modified full-face" look so that standard wheel weights could be attached thereto in the usual manner, a separate trim ring was needed to complete the "full-face" styling effect. These compromises also added to the cost and complexity of the complete wheel. An example of use of such a trim ring and "POLYCAST" construction is shown in the Spisak U.S. Pat. No. 3,891,276.
It has also been difficult if not impossible to achieve a placement of wheel vent windows in the outboard face of the urethane body of the "POLYCAST" wheel disposed radially outwardly close to the outboard tire bead retaining flange of the wheel. This is particularly true if a large number of small vent openings and/or extreme shape effects were desired for styling purposes, such as in simulating certain "scoop-spoke" effects, due to the negative draft angles and other imitations involved in the urethane "POLYCAST" molding process and apparatus. Thus the practice hitherto in making vent windows in "POLYCAST" wheels has been to have the mold vent fingers (such as bosses 46 and/or pedestal portions 294 of the aforementioned U.S. Pat. No. 3,762,677) protrude upwardly from a lower mold part so as to penetrate the "windows" in the steel backbone or disc of the metal portion of the wheel to provide a brake ventilation air passage which extends completely through the wheel.